allow Eth1 monitor to run without genesis_deposit_contract_snapshot.ssz (#3279)

beacon_chain/eth1/eth1_monitor.nim

@@ -868,11 +868,35 @@ proc init*(T: type Eth1Chain, cfg: RuntimeConfig, db: BeaconChainDB): T =
     finalizedBlockHash: finalizedDeposits.eth1Block,
     finalizedDepositsMerkleizer: finalizedDeposits.createMerkleizer)
 
+proc createInitialDepositSnapshot*(
+    depositContractAddress: Eth1Address,
+    depositContractDeployedAt: BlockHashOrNumber,
+    web3Url: string): Future[Result[DepositContractSnapshot, string]] {.async.} =
+
+  let dataProviderRes =
+    await Web3DataProvider.new(depositContractAddress, web3Url)
+  if dataProviderRes.isErr:
+    return err(dataProviderRes.error)
+  var dataProvider = dataProviderRes.get
+
+  let knownStartBlockHash =
+    if depositContractDeployedAt.isHash:
+      depositContractDeployedAt.hash
+    else:
+      try:
+        var blk = awaitWithRetries(
+          dataProvider.getBlockByNumber(depositContractDeployedAt.number))
+        blk.hash.asEth2Digest
+      except CatchableError as err:
+        return err(err.msg)
+
+  return ok DepositContractSnapshot(eth1Block: knownStartBlockHash)
+
 proc init*(T: type Eth1Monitor,
            cfg: RuntimeConfig,
            db: BeaconChainDB,
            web3Urls: seq[string],
-           depositContractSnapshot: DepositContractSnapshot,
+           depositContractSnapshot: Option[DepositContractSnapshot],
            eth1Network: Option[Eth1Network],
            forcePolling: bool): T =
   doAssert web3Urls.len > 0
@@ -881,7 +905,8 @@ proc init*(T: type Eth1Monitor,
   for url in mitems(web3Urls):
     fixupWeb3Urls url
 
-  putInitialDepositContractSnapshot(db, depositContractSnapshot)
+  if depositContractSnapshot.isSome:
+    putInitialDepositContractSnapshot(db, depositContractSnapshot.get)
 
   T(state: Initialized,
     depositsChain: Eth1Chain.init(cfg, db),
@@ -911,6 +936,19 @@ proc resetState(m: Eth1Monitor) {.async.} =
     await m.dataProvider.close()
     m.dataProvider = nil
 
+proc ensureDataProvider*(m: Eth1Monitor) {.async.} =
+  if not m.dataProvider.isNil:
+    return
+
+  let web3Url = m.web3Urls[m.startIdx mod m.web3Urls.len]
+  inc m.startIdx
+
+  m.dataProvider = block:
+    let v = await Web3DataProvider.new(m.depositContractAddress, web3Url)
+    if v.isErr():
+      raise (ref CatchableError)(msg: v.error())
+    v.get()
+
 proc stop(m: Eth1Monitor) {.async.} =
   if m.state == Started:
     m.state = Stopping
@@ -1112,20 +1150,14 @@ proc startEth1Syncing(m: Eth1Monitor, delayBeforeStart: Duration) {.async.} =
   if delayBeforeStart != ZeroDuration:
     await sleepAsync(delayBeforeStart)
 
-  let web3Url = m.web3Urls[m.startIdx mod m.web3Urls.len]
+  await m.ensureDataProvider()
-  inc m.startIdx
+  let
+    web3Url = m.web3Urls[(m.startIdx + m.web3Urls.len - 1) mod m.web3Urls.len]
+    web3 = m.dataProvider.web3
 
   info "Starting Eth1 deposit contract monitoring",
     contract = $m.depositContractAddress, url = web3Url
 
-  m.dataProvider = block:
-    let v = await Web3DataProvider.new(m.depositContractAddress, web3Url)
-    if v.isErr():
-      raise (ref CatchableError)(msg: v.error())
-    v.get()
-
-  let web3 = m.dataProvider.web3
-
   if m.state == Initialized and m.eth1Network.isSome:
     let
       providerNetwork = awaitWithRetries web3.provider.net_version()
@@ -1239,6 +1271,7 @@ proc start(m: Eth1Monitor, delayBeforeStart: Duration) =
         if runFut.error[] of CatchableError:
           if runFut == m.runFut:
             warn "Eth1 chain monitoring failure, restarting", err = runFut.error.msg
+            m.dataProvider = nil
             m.state = Failed
         else:
           fatal "Fatal exception reached", err = runFut.error.msg

beacon_chain/nimbus_beacon_node.nim

@@ -119,11 +119,20 @@ proc init*(T: type BeaconNode,
            depositContractDeployedAt: BlockHashOrNumber,
            eth1Network: Option[Eth1Network],
            genesisStateContents: string,
-           genesisDepositsSnapshotContents: string): BeaconNode {.
+           depositContractSnapshotContents: string): BeaconNode {.
     raises: [Defect, CatchableError].} =
 
   var taskpool: TaskpoolPtr
 
+  let depositContractSnapshot = if depositContractSnapshotContents.len > 0:
+    try:
+      some SSZ.decode(depositContractSnapshotContents, DepositContractSnapshot)
+    except CatchableError as err:
+      fatal "Invalid deposit contract snapshot", err = err.msg
+      quit 1
+  else:
+    none DepositContractSnapshot
+
   try:
     if config.numThreads < 0:
       fatal "The number of threads --numThreads cannot be negative."
@@ -199,6 +208,24 @@ proc init*(T: type BeaconNode,
     fatal "--finalized-checkpoint-block cannot be specified without --finalized-checkpoint-state"
     quit 1
 
+  template getDepositContractSnapshot: auto =
+    if depositContractSnapshot.isSome:
+      depositContractSnapshot
+    elif not cfg.DEPOSIT_CONTRACT_ADDRESS.isZeroMemory:
+      let snapshotRes = waitFor createInitialDepositSnapshot(
+        cfg.DEPOSIT_CONTRACT_ADDRESS,
+        depositContractDeployedAt,
+        config.web3Urls[0])
+      if snapshotRes.isErr:
+        fatal "Failed to locate the deposit contract deployment block",
+              depositContract = cfg.DEPOSIT_CONTRACT_ADDRESS,
+              deploymentBlock = $depositContractDeployedAt
+        quit 1
+      else:
+        some snapshotRes.get
+    else:
+      none(DepositContractSnapshot)
+
   var eth1Monitor: Eth1Monitor
   if not ChainDAGRef.isInitialized(db).isOk():
     var
@@ -207,7 +234,7 @@ proc init*(T: type BeaconNode,
 
     if genesisStateContents.len == 0 and checkpointState == nil:
       when hasGenesisDetection:
-        if genesisDepositsSnapshotContents.len > 0:
+        if depositContractSnapshotContents.len > 0:
           fatal "A deposits snapshot cannot be provided without also providing a matching beacon state snapshot"
           quit 1
 
@@ -224,7 +251,7 @@ proc init*(T: type BeaconNode,
           cfg,
           db,
           config.web3Urls,
-          depositContractDeployedAt,
+          getDepositContractSnapshot(),
           eth1Network,
           config.web3ForcePolling)
 
@@ -346,16 +373,12 @@ proc init*(T: type BeaconNode,
             headStateSlot = getStateField(dag.headState.data, slot)
       quit 1
 
-  if eth1Monitor.isNil and
+  if eth1Monitor.isNil and config.web3Urls.len > 0:
-     config.web3Urls.len > 0 and
-     genesisDepositsSnapshotContents.len > 0:
-    let genesisDepositsSnapshot = SSZ.decode(genesisDepositsSnapshotContents,
-                                             DepositContractSnapshot)
     eth1Monitor = Eth1Monitor.init(
       cfg,
       db,
       config.web3Urls,
-      genesisDepositsSnapshot,
+      getDepositContractSnapshot(),
       eth1Network,
       config.web3ForcePolling)